www.kr-2s.com

Hi. I am the guy who built the jig in question. You are absolutely right about pre-aligning the hole before drilling through. What the photo does not show is that 4130N steel WAFs (wing attachment fittings) are used to join the inner and outer spars. These WAFs have holes drilled and it is these holes that the jig aligns on either side of the spar. Whilst the WAFs are not 100% complete, you may get an idea of what I am talking about here http://www.kr-2s.com/wafs.html To align the jig, you pass a same size drill bit (3/16") through the opposite side and poke it into a WAF drill hole. Hold another WAF on the opposite side of the spar and start drilling through the jig and matching WAF hole. Unfortunately, I have had to place a ban on people linking directly to pictures on my site but you can see the jig at the bottom of this page. http://www.kr-2s.com/spar.html Happy building.